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Chen F.,Shanghai University | Di Q.,Shanghai University | Yuan P.,Shanghai Hailong Petroleum Tubular Goods Research Institute | Wang W.,Shanghai University | And 3 more authors.
Shiyou Xuebao/Acta Petrolei Sinica

The difficulty in carrying cuttings is a universal problem encountered in drilling of highly deviated and extended reach directional wells or horizontal wells, and it significantly affects the safety and efficiency of drilling operation. We developed an effective hydroclean drill pipe (EHCDP) and studied flow behaviors of the annulus flow field with EHCDP by applying a realistic model technique of the computational fluid dynamics (CFD). Numerical simulation data were analyzed in terms of flow diagrams, velocity field, and pressure field, and the EHCDP mechanism was studied by examining the effect of a spiral groove structure on flow behaviors of the annulus fluid. The results show that fluid can form a vortex cavity near spiral grooves with EHCDP, which can effectively change flow behaviors of fluid in an eccentric annulus, resulting in the annulus fluid to move from the low-side of an annulus to the up-side of that, which will transport cuttings to the up-side of an annulus as well. In addition, the vortex near grooves will swirl cuttings into spiral grooves, then cuttings will be thrown into the up-side of an annulus with centrifugal force produced by rotation of a drill pipe, therefore, cuttings beds at the bottom hole can be effectively removed. Source

Lei H.-Y.,Peking University | Lei H.-Y.,Petrochina | Wang H.-Y.,Peking University | Wang H.-Y.,Petrochina | And 4 more authors.
Jilin Daxue Xuebao (Diqiu Kexue Ban)/Journal of Jilin University (Earth Science Edition)

Pyrolysis kinetics characteristics of oil shale samples obtained from Liushuhe basin were investigated by Rock Eval analysis. The pyrolysis characteristics were studied at different heating rates (10, 15, 20, 25, 30°C/min) from 200°C to 600°C. Based on the Friedman mathematical formula and Sestak reaction mechanism, the reaction activation energy and reaction function were obtained, and so the pyrolysis mathematical model was developed. This mathematical model can be used to calculate the hydrocarbon conversion and required times for the fixed conversion. It is found that the reaction activation energy is not a constant and is a variable with the variety of reaction temperature. The reason is that the pyrolysis reaction process of oil shale is complicated multistep reaction, in which reaction mechanism is variable in different temperature range. Source

Gao Q.,Tsinghua University | Sun C.,Tsinghua University | Yang C.,China Petroleum Materials Corporation
International Journal of Human-Computer Interaction

The potential of microblogging networks to spread information, ideas, and influence via social links has been recognized. Individuals at central or critical positions in the microblogging networks are expected to play an important role in spreading information, but this belief must be tested with empirical investigations in actual information dissemination. Furthermore, it is possible that individuals with different types of structural importance influence the information dissemination in different ways. This article examines the impact of five structural properties (degree, betweenness, closeness, tie strength, and k-value) on information dissemination capabilities by tracking the dissemination of 150 messages in Sina Weibo. The results highlight the importance of betweenness centrality, which best explains the influence on information dissemination distance and coverage size. It also best predicts the information dissemination efficiency. Degree centrality is found to be a strong predictor of one's influence among immediate followers. Tie strength negatively correlates with influence on the information dissemination distance and coverage size. These structural properties address different aspects of the information dissemination power and should be used in a complementary way when planning information dissemination strategies in microblogging systems. Copyright © Taylor & Francis Group, LLC. Source

Hu B.,China University of Petroleum - Beijing | Zhu H.,China University of Petroleum - Beijing | Ding K.,China Petroleum Materials Corporation | Xu F.,China University of Petroleum - Beijing | Zhang Y.,China University of Petroleum - Beijing
Journal of Mechanical Science and Technology

This study focuses on the heat transfer characteristic of a horizontal subsea Xmas tree assembly at a high spatial resolution. Computational fluid dynamics (steady Reynolds-averaged Navier-Stokes) in combination with Low Reynolds number modelling (LRNM) is adopted for heat transfer analysis, which has been validated against a full scale underwater gate valve heat transfer experiment with good agreements. The characteristics of cold sea water flowing through the subsea tree, and of convection heat transfer between the subsea tree and ambient cold water are obtained. The typical “hot spots,” which have high Convection heat transfer coefficient (CHTC) and create great large amounts of heat loss, are numerically determined. Under the designed water depth, the effects of installation orientation, sea water velocity, and inner oil temperature on convection heat transfer are investigated as well. Such work is significant for thermal design of the subsea tree to increase structural reliability and flow assurance level. © 2015, The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg. Source

Hu B.,China University of Petroleum - Beijing | Zhu H.,China University of Petroleum - Beijing | Ding K.,China Petroleum Materials Corporation | Zhang Y.,China University of Petroleum - Beijing | Yin B.,China University of Petroleum - Beijing
Applied Ocean Research

The conjugate heat transfer of an underwater gate valve assembly is numerically investigated by 3D steady RANS CFD approach. Different schemes of turbulence models in combination with near-wall treatments including low Reynolds number modeling (LRNM) and wall functions (WF) are adopted in simulations. An underwater gate valve heat transfer experiment with the same scale of the computational model is conducted for validation. It is found that the realizable k-ε turbulence model in combination with LRNM is the most appropriate numerical scheme to solve the underwater conjugate heat transfer problem. Based on the simulation results, the flow and heat transfer characteristics of the underwater gate valve assembly are discussed. The temperature and convection heat transfer coefficient (CHTC) distribution are distinct on both windward and leeward surfaces affected by the flow field. The numerical approach is also promising for conjugate heat transfer calculation of similar subsea thermal-fluid system. © 2016 Elsevier Ltd. Source

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